This invention relates to an oil circulating system for marine propulsion apparatus including a lower gear case unit housing interconnecting drive shaft and propeller shaft gearing, and in particularly to an outboard motor including a bevel gear coupling in the lower unit.
Relatively small boats such as recreational power boats widely employ an outboard motor secured to the transom for driving of the boat. More recently inboard-outboard assemblies have been employed for driving of propeller to provide similar propulsion. Generally, in such propeller driven marine propulsion drive systems, a detachable lower unit forms a part of the driving housing of the propulsion apparatus, said unit including a housing closely fitting around a horizontally directed propeller shaft coupled to a vertical drive shaft through suitable coupling gears, generally in the form of bevel gears fixed respectively to the propeller shaft and to the drive shaft. A direct reversing drive can be readily provided by providing a pair of bevel gears rotatably mounted on the propeller shaft and mating with opposite sides of a pinion bevel gear mounted to the lower end of the drive shaft. The opposing faces of the propeller shaft mounted bevel gears are selectively engaged by a drive member fixed to rotate with the propeller shaft. The bevel gears rotate in opposite directions and thus provide a direct reversing drive by selective positioning of the engaging drive member on the propeller shaft.
Generally, the drive shaft is secured within a vertical housing forming a part of the lower unit and most generally integrally formed as a part of the lower gear housing. The shaft is suitably supported by vertically spaced bearings mounted in an opening or chamber in the lower unit housing, which bearings support the drive shaft in driving relationship to the propeller shaft.
It is important to maintain proper lubrication of the gears and the shaft bearing. It is general practice to maintain the gear case totally filled with a suitable lubricating oil to assure adequate lubrication and minimize any entry of water. Further, the lower units are usually formed with some interconnecting passageway between the gear casing portion immediately adjacent the coupling gears and the chamber housing the bearing supports for the drive shaft.
For example, expired U.S. Pat. No. 2,549,477 shows an early lubrication system wherein an inlet oil passage was located adjacent the periphery of the bevel gear on the vertical drive shaft with the centrifugal forces thereof throwing the oil into the passage and thereby causing it to move upwardly and through an interconnecting passageway into the chamber housing the drive shaft bearings. More recently, the inlet passageway has been located immediately above the meshing gears on the common plane through the centers of the vertical shaft and the propeller shaft, relying on the meshing or collapsing of the mating gear teeth to force the oil upwardly through the inlet passageway to the drive shaft chamber, with a suitable return provided to the gear chamber.
Although such systems have provided satisfactory operation, they generally require complete filling of the gear case unit with oil. Further, it has been found desirable to increase the circulation of the oil upwardly through the bearing supports for the drive shaft to maintain optimum lubrication thereof.